1. Field of the Invention
The present invention relates to an optical lens system for taking image, and more particularly to a four-lens type optical lens system for taking image used in a mobile phone camera.
2. Description of the Prior Art
In recent years, with the popularity of mobile phone camera, the optical lens system for taking image has been becoming thinner and thinner, and the electronic imaging sensor of a general digital camera is typically a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) sensor. Due to advances in semiconductor manufacturing, the pixel size of sensors has been reduced continuously, and miniaturized optical lens systems for taking image have increasingly higher resolution. Therefore, there's increasing demand for image quality.
A conventional high resolution mobile phone camera usually takes the form of “front aperture stop”, and this kind of mobile phone camera generally requires four lens elements for high resolution: the first and second lens elements are usually two glass lens elements with a spherical surface that are glued to each other to form a Doublet for eliminating chromatic aberration. However, this method has the following disadvantages:
First, the arrangement of too many spherical lens elements reduces the degree of freedom of the optical system, and as a result, reducing the length of the whole optical system is difficult.
Second, the gluing process of the glass lens elements is difficult to control.
The present invention mitigates and/or obviates the afore-mentioned disadvantages.